YJ-91

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YJ-91 is the Chinese version of Kh-31, with YJ short for Ying Ji (Yingji, 鹰击) meaning Eagle Strike. After purchasing 200 Kh-31P from Russia, China decided to develop their own version because the original Kh-31 missile did not fully satisfy Chinese requirement. The resulting YJ-91 missile is developed by Hongdu Aviation Industry Corporation, the same manufacturer of Silkworm missile.

[edit] YJ-91 Anti-radiation missile

The anti-radiation version of the YJ-91 missile is developed from Kh-31P, which must use a wide arrays of seekers to cover the entire radar frequency bands. Chinese were not satisfied with the need to have multiple seekers and would have preferred to have a single seeker capable of covering multi frequency bands, like that of AGM-88 HARM. However, such ambition proved to be too great for the Chinese microelectronics industry and could not achieve the goal in a single step within the required original timeline specified by the Chinese military. Instead, a two-step approach was implemented: the completion of the development of a single seeker covering multi frequency band was pushed back, while a stopgap measure was adopted in the meantime: Kh-31P was modified so that the seekers could be rapidly changed in the forward airstrips (providing the specialized tooling is present) so that missile would not need to be sent back to depots or factories to perform such operation.

The resulting anti-radiation version of YJ-91 missile has a slightly increased range to 120 km in comparison to 110 km of the original Kh-31P. In addition to developing a seeker that covers multiple frequency band similar to that of AGM-88 HARM, additional measures to upgrade the missile are also in development concurrently, and open software architecture is a featured adopted in the development. Some of the measures reportedly included prioritizing threats, which could uploaded to computer onboard the missile on the ground or by the pilots while in flight so that threats could be updated in real time, but such ambitious goal would not be ready until the seeker covering multiple frequency bands is completed.

[edit] YJ-91 Anti-ship missile

Chinese have also developed the anti-ship version of YJ-91 missile. However, this version was completely indigenous developed by Chinese themselves from Kh-31P anti-radiation missile, instead of Kh-31A anti-ship missile, which China did not order any. Chinese felt that the original Kh-31A could not fully satisfy their requirement because the high-low trajectory of the missile meant early detection, thus it is prone to interception. In contrast, the low-low trajectory usually adopted by the subsonic anti-ship missiles would better utilize the supersonic speed of Kh-31A, since such trajectory shorten the detection range and the high speed would reduce the target’s reaction time once the missile is discovered at much closer range. As a result, China did not place any order of Kh-31A anti-ship missile and decided to indigenously develop their own equivalent to incorporate sea-skimming capability based on the experience gained from Kh-31P anti-radiation missile.

The resulting anti-ship version of YJ-91 missile incorporated sea-skimming capability that the cruising altitude is no more than 20 metre above the sea level. At the terminal attack stage (usually after the active radar seeker of the missile is turned on), the missile would further drop to 7 metre above the sea level for the final phase. This attack altitude could be further decreased to just 1.2 metre above the sea level when sea state allows, and alternatively, the missile could also be programmed to have the popup-and-dive attack mode like that of Boeing Harpoon. However, such sea-skimming capability come at a price at the expense of the maximum range: in comparison to the original 70 km range of Kh-31A, the maximum range of YJ-91 anti-ship missile is reduced by more than a quarter to 50 km in sea-skimming mode. Like the anti-radiation version, it is reported that many planned upgrades are currently in development. An application for research grants to develop a submerged launched version of YJ-91 anti-ship missile had once appeared at Chinese websites on the internet, indicating China is attempting to develop a version for its submarine fleet.

[edit] Specifications

• Length: 4.7 metre
• Diameter: 0.3602 metre
• Weight: 600 kg
• Warhead: 90 kg
• Speed: > Mach 3
• Minimum range: 5 km
• Maximum range: 50 km (anti-ship version), 120 km (anti-radiation version)
• Engine: ramjet with solid rocket fuel booster
• Guidance: active radar homing (anti-ship version) & passive radar homing (anti-radiation version)
• Developer: Hongdu Aviation Industry Corporation